Estonian Alvars and Juniper Shrublands—Instructions for the Management and

Restoration of CommunitiesA brief translated summary of the manual compiled by Aveliina Helmi in 2009. The list of materials used and references can be found in the original manual. (http://www.keskkonnaamet.ee/public/PLK/Lisa_2_Loopealsete_ja_kadastike_hoolduskava_2011.pdf)

Overview of Estonian Alvars

Alvars are semi-natural grasslands with a thin layer of lime-rich soil which is generally less than 20 (30) cm deep. Alvars are semi-natural ecosystems that are also known as heritage communities. This means that their formation and persistence is closely connected to human activity, mainly grazing.

Most Estonian alvars have formed secondarily due to deforestation and subsequent grazing. The herb layer of alvars that are in a good condition is short, not very productive and diverse, consisting mainly of stress-tolerant plants that prefer calcareous soils. Junipers mostly grow on alvars, either separately or in groups; nowadays, there are no completely treeless alvars in Estonia. Grazed alvars tend not to have a tree layer, or, if they do have one, it consists of solitary specimens. However, trees will grow easily on non-grazed alvar grasslands with deeper soil.

Alvars are not widespread in the world, which makes them globally rare, and, therefore, these communities also need special protection. In addition to Estonia, a considerable number of alvars can only be found on large Swedish islands, mainly on Öland and Gotland. In Estonia, alvars are mainly distributed in areas with exposed limestone bedrock in Saaremaa, Muhu, Läänemaa and Hiiumaa, but also in Harjumaa and Ida- and Lääne-Virumaa (see figure 1 and 2).

Figure 1: Alvars in Europe

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Figure 2: Historical distribution of alvars in Estonia

In 1930s, there were 43,000 hectares of alvar grasslands in Estonia (Figure 2). During the inventories of 1978 and 1981, approximately 16,000 hectares of alvar communities were registered, 25% of which were more or less being encroached by forest. Nowadays, there are less than 12,000 hectars of alvars preserved in Estonia, only 3,000 of which can be deemed representative (see figure 3).

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Figure 3: Current distribution of alvars in Estonia, more representative areas are marked with red

Environmental Conditions on Alvars

Alvars’ alkaline soil is very thin, therefore the plants that grow there are suffering from a lack of nutrients. Thus, the common species that inhabit alvars have restricted growth and require considerably less nutritious soil. In summer, thin-soiled alvars are characterised by a completely dried out soil due to the wind and sun.

Figure 4: Polygons formed by frost heaving in thin-soiled alvar community

Flora and Fauna on Alvars

Thanks to the extensive fluctuation of microclimatic environmental conditions, alvars are home to plant species from different geographic regions: South-Siberia and South-East European steppes (rock wormwood, spring cinquefoil, purple milk-vetch, mountain clover, carline thistle, dyer’s woodruff, snowdrop anemone), North-European subarctic (Alpine mouse-ear chickweed, Alpine meadow-grass, Alpine cinquefoil) and North-West European oceanic climate (rue-leaved saxifrage, white stonecrop, etc.). The number of vascular plant species in Estonia that are ecologically suitable for alvars is 267 (17% of domestic flora). 16% of the species are under protection.

Development of Species Richness in Alvars and its Conservation

By the number of vascular plants, alvars are the second most species rich communities in Estonia after wooded meadows. Behind its current species richness lies the long-time effect of human activity and the historically extensive coverage of alvars. Human impact and wide coverage formed the network of connected habitat patches, which facilitates the dispersal of vascular plants between different alvar patches. However, the smaller the habitat patches

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become and the further they remain from each other due to the habitat loss and fragmentation, the less probable it is for the species to disperse between individual habitat patches and thus maintain their historical species richness. At the moment, despite the vast loss of habitat area and increased isolation, the alvars in Saaremaa are as species rich as they have been historically. However, this means that our alvars are suffering from the so-called extinction debt. Extinction debt is imposed on the species that manage to temporarily defy unsuitable environmental conditions (such as too small area and increased isolation) and stay viable for a shorter or longer period after the fragmentation of the community. However, as long as unsuitable conditions persist, these species are doomed to extinction in the future.

Factors Endangering Alvars. Overgrowth

Since 1930s and throughout the Soviet era, grazing on alvars decreased considerably, which has brought along the encroachment by shrubs (mainly junipers), trees (mainly pines) and the invasion of tall grazing-sensitive herbaceous plants.

Figure 5: overgrown alvar on Muhu.

Still, not even thin-soiled and almost platy alvars are not safe from overgrowth

Figure 6: Thin soil does not prevent overgrowth.

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During 1950s, an extensive afforestation programme (on approximately 25,000 hectares) was carried out in Saaremaa, which succeeded on 6,000 hectares of alvars. Fertilisation is very dangerous to alvars.

Figure 7: The result of the afforestation attempt at Lõo alvar, Saaremaa.

Protection of Alvars

Alvars are a priority habitat type in the framework of NATURA 2000 (Habitats Directive Annex 1 habitat type *6280 and also *8240). Estonia is home to a considerable number of the world’s alvars (28%). Inactivity will lead to the complete disappearance of alvars already in the next decade. The organisation of alvar conservation is not very advanced in Estonia. Europe’s largest alvar formation Great Alvar (Stora Alvaret; 26,000 hectares) on the island of Öland, Sweden is in the list of UNESCO World Heritage sites

Figure 8: Restored alvar on the island of Öland, Sweden.

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Landowners’ initiative in relation to the management of alvars should be supported in all manners. Alvars are the type of community which could nowadays bring financial profit from its semi-natural functioning by producing so-called meadow meat and via agri-environmental subsidies for the management of heritage communities.

Alvar Management

First of all, following aspects should be kept in mind in relation to alvar management. (1) Alvars are semi-natural communities, which, in order to persist as an open community for a long period of time, need moderate human influence—grazing.

Figure 9: Grazing with suitable intensity ensures the preservation of an alvar.

(2) It is useful to switch between the types of livestock (sheep/cows/horses/goats) as well as the grazing intensity in every few years. This allows species with different needs to settle in the areas, since different animals prefer different forage. (3) Because of extinction debt, it is very important to ensure the spread of both plant and animal species between habitat patches or, in other words, to re(create) the network of habitat patches. (4) Activities which damage topsoil should not be allowed (driving motor vehicles, self-made campfires, ploughing, milling, afforestation)! Excessive damage to herb layer makes the preservation or restoration of the alvar community highly unlikely. Recreational activities—camping, hiking and walking, field trips—should be promoted.

Grazing as the Most Effective way to Conserve Alvars

In case of suitable grazing intensity, the herd will consume 50% of the biomass available, which means that at least half of the pasture must be characterized by very low herb layer (ca 5 cm in dry alvar grasslands and 10 cm in temporarily wet alvar grasslands). While

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determining the intensity, one should take into account the energy value of meadow grass as well as the energy needs of the grazing animals.

Tor-grass is an exceptionally good indicator species of the poor condition of the community long before the spread of shrubs.

Figure 10: Deep-soiled alvar in Saaremaa. If this is also grazed, the intensity is clearly too low.

On deep-soiled alvars, the wide spread of low and light-demanding species and dense herb layer undamaged by trampling indicate long-term grazing with suitable intensity. Indicator species of good light conditions are, for instance, pink pussy-toes, rockrose, wild thyme, milkwort, little mouse-ear, common kidneyvetch, spring cinquefoil, dyer’s woodruff, vernal sedge (see Table 2). In case of excessive grazing, the more palatable species will be eaten wholly, topsoil will suffer from trampling, excessive manure will overfertilise the community and the species richness of vascular plants will reduce.

Figure 11: occasionally overgrazed area in Läänemaa, Penijõgi.

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Different Types of Alvars and Their Management

In Estonia, a classification of alvars has been compiled on the basis of mathematical analyses, where one can distinguish roughly three different types of alvars according to moisture conditions and soil thickness.

1) Temporarily wet or Molinietum-type alvars. These are mainly distributed along the temporarily wet areas on Saaremaa and in South-West Estonia. Characteristic vascular plant species are purple moor grass, blue moor grass, carnation sedge, blue sedge, northern bedstraw, common tormentil. These alvars are not very rich in species and their productivity is relatively high. They are well suited for grazing and the management is based on the same principles as those of the Avenetum-type (see point 2).

Figure 12: Moist Molinietum-type alvar.

2) Dry deeper soil layer or Avenetum-type alvars. Characteristic vascular plant species are meadow oat-grass, fern-leaf dopwort, mountain clover, common kidneyvetch, quaking-grass mouse-ear hawkweed, dwarf thistle, lady’s bedstraw, blue moor grass, purple milk vetch,

spring cinquefoil, carline thistle, sheep fescue, lady’s mantle, wild thyme and many others.

Figure 13: Managed Avenetum-type alvar.

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The Avenetum-type alvar is the most rich in species and it is also the community type which depends on diligent grazing the most. With suitable grazing intensity, these kinds of communities will become only richer in species; if grazing is discontinued, they will quickly be encroached by junipers.

Figure 14: Dense grassland herb layer characteristic to an alvar in good condition.

In order to conserve/restore the alvar grassland diversity, the recommended optimum number of grazing sheep is 1.6–3.5 sheep per one hectare (0.2–0.5 livestock units per hectare), up to 1 livestock unit per hectare (up to 6 sheep on a hectare) on deep-soiled alvars. In North-Estonian highly productive alvar areas, the grazing intensity could be approximately 1 livestock unit per hectare.

Figure 15: North-Estonian version of Avenetum-type alvars (Võle alvar).

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Heath alvar grassland subtype—distributed in areas with more sandy soil, often in sand ridges near the sea. Characteristic species are thyme-leaved sandwort, bulbous buttercup, vernal sedge, brown bent and ling heather. Shingle alvars subtype—appears in areas where thin soil and vegetation is not able to cover the limestone scree and shingle.

Figure 16: Developing community on scree ridges in Kassari, Hiiumaa.

3) Dry thin soil layer type or Festucetum-type alvars (also plate-alvar). Community with a thin soil layer (<5 cm), where there are patches free from vegetation covered with soil that are caused by frost heaving; these may occur similarly to areas with platy alvar. Festucetum-type alvar grasslands represent an extremely rare plant community and are home for a number of phytogeographically rare plants and those that inhabit the border of their natural habitat, therefore it is of great importance in terms of nature conservation. Characteristic species are sheep fescue, northern wormwood, rock wormwood, white stonecrop, goldmoss stonecrop, knotted pearlwort, basil thyme, etc. These areas are suitable for grazing sheep. Thin-soiled alvar grasslands have sparse vascular plant layer, therefore, these areas are not valued as pastures for larger animals. However, thin soil layer does not prevent overgrowing with shrubs and trees and the traditional management via grazing is necessary.

Figure 17: Dry thin-soiled Festucetum-type alvar in Atla village, Saaremaa.

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Where there are plenty of wild orchids, measures should be taken to conserve them. Most of the orchids require moderate management and an open community in order to sustain themselves, but very intense sheep grazing may decrease the populations size of orchids.

Restoration of Alvars. The Goals of the Restoration of Estonian Alvars

Alvar studies have shown that it is necessary to conserve as many alvars as possible, which should also involve re-creating a network of alvar areas. Creating solitary representative alvar conservation sites is not enough, since most grassland species need to exchange genetic material between the populations of different habitat sites in order to sustain them for a long period of time. The overgrowth processes are not entirely irreversible and even an alvar that is visually in a rather bad state can be restored. A sudden drop in species richness and significant changes in the species that make up the grass layer will take place once the shrub coverage is more than 75–80%. At this coverage, the light conditions will quickly change, the dense herb layer characteristic to alvars will disappear and light-demanding trampling-resistant plant species will at first be replaced by the shade-tolerant species characteristic to alvar forests. Most Estonian alvar areas can still be restored, since the regional species pool has been preserved in its entirety. Alvars with less than 75–80% juniper coverage and well-preserved herb layer should be the first ones to be restored. Since the alvars in different Estonian regions are valuable with respect to different aspects, it would be good to find regional centres in Eastern Harjumaa, Keila, Western Estonia, Pärnumaa, Hiiumaa, Muhu, Eastern Saaremaa and Western Saaremaa.

Alvar Restoration Activities

Most of the experience in the restoration of alvars comes from Sweden. 1996 saw the start of European Union LIFE project on the island of Öland, in the course of which more than 7,000 hectares of alvars have been restored. Juniper scrub (also broad-leaved tree scrub, if present) must be removed from as close to the ground as possible during the restoration process. Nowadays, the cheapest way to do it is by using a shrub cutter and a saw, or during large-scale restoration, specific heavy machinery can be used.Restoration work can be done from the late summer until the beginning of spring. The nesting season in spring and early summer is not suitable for restoration work. In case of dry thin soil layer type alvars (trampling sensitive), the restoration work should take place at a more wet time, in autumn and winter. It is very necessary to start grazing after the restoration. It is particularly necessary on excessively overgrown areas where the local species pool characteristic to alvars has already reduced or disappeared, otherwise the area cleared of junipers will be encroached by weeds and plants from more fertile habitats.

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Currently (2011), a great number of Estonian alvars are in a state where the local species pool is still preserved, but the cover of junipers is already too extensive. Clearing the area from junipers is the only way to save a great part of alvar areas from further overgrowth and to gain extra time to organise the suitable management.

Figure 18: Here we can see an alvar restored from a juniper scrub, which has not been grazed after the clearing of junipers. As a result, it has been colonized by pioneer weed species.

Aim of the restoration is to create open habitat with ca 30% coverage of shrubs, located sparsely on the site. Sparse shrub cover will allow light conditions to be suitable for light-demanding grassland plants, while offering wind- and sun-shade for both invertebrates and grazing animals. If the area has patches of older ‘juniper forest’, then these could definitely be preserved as they are. However, it should be kept in mind that a managed/restored alvar that is seen as one area should not include dense shrub or tree patches larger than 1,000 m².

Juniper communis shrublands in Estonia

Estonian juniper shrublands can be divided roughly in two: juniper scrubs that are situated on former alvars (alvar shrublands) and juniper scrubs which have been formed as the result of overgrowing of other types of grasslands (boreal, boreal heath, and dry and fresh grasslands), but also clearings or fallow fields becoming encroached by juniper. Primarily formed juniper shrublands can be found in small numbers on scree ridges near the sea. It is possible that none of the Estonian juniper shrublands are climax communities; instead they are successional (unstable) communities before the formation of a forest community. The distribution of juniper shrublands has not been mapped. Henceforth, a loose classification has been used: ‘alvar juniper shrublands’ and ‘other type of shrublands’, since the juniper coverage limits and management manuals assigned to those areas differ.

Alvar Juniper Shrublands

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Alvar shrubland is a successional stage between an open alvar (Natura 2000 habitat type *5130) which is being managed by grazing and a coniferous alvar forest which is a climax community (Natura 2000 code *9010). Alvar juniper shrublands differ from the other shrublands formed from grasslands by calcareous soil that is thinner than 30 cm. Juniper scrublands that have formed in previously open alvars, have been assigned to the Natura 2000 habitat type 5130 (Juniperus communis formations on heaths or calcareous grasslands) according to the Habitats Directive manual.

Still, it is important to stress that the area in the danger of overgrowing should be considered an alvar (habitat type *6280) and not a shrubland (5130) if it meets all of the following requirements: (1) the previous condition of the area has been an open alvar (2) soil thickness (without needle-fall) is less than 30 cm (3) patches of preserved grassland herb layer consists of species characteristic to open alvars (4) juniper coverage is less than 75–80% and the light conditions are still good at some spots (see also Table 1). If the juniper coverage is 30–50%, it can be considered a relatively open alvar with all features characteristic to alvars. In this case, the first thing to do is to start grazing and removing excessive junipers. Secondly, if we consider 50–70% of juniper coverage also as habitat type *6280, we reserve the opportunity to restore the valuable open alvar grasslands and manage them in the future. The percentage of light-demanding grassland species in the community will quickly drop if the juniper coverage (or pine canopy cover) is 75–80%; this is why this area can be justly considered as an alvar before that coverage percentage is reached. Restoration of shrublands with less than 80% juniper cover to a more open community is fruitful and advisable at any given opportunity. In order not to risk the destruction of alvars and the extinction of the species that inhabit them, we must firstly restore and manage as many alvar grasslands (habitat type *6280) as possible.

Other Type of Juniper Shrublands

Juniper shrublands do not always originate of alvars. In addition to alvars, other semi-natural grasslands may become encroached by junipers: dry boreo-nemoral grasslands and sandy-soiled dry boreal heath and boreal grasslands. Juniper thickets can also form on abandoned farmlands, clearings, etc. In Western Estonia, cleared alvar forests often become shrublands. The juniper scrubs on scree ridges risen from the sea as primary communities (for instance on Hiiumaa, the island of Suur-Pakri) have formed entirely naturally.

Restoring Grasslands from Juniper Shrublands

In case of dire need it is possible to restore the previous community type also in areas with more than 80% of juniper coverage. This should be done especially if the grassland characteristic herb layer is preserved, the juniper coverage has not yet reached 100% and grassland species can still be found in the vicinity. In case of restoring these areas, juniper

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removal during several years is justified. Juniper cover should be reduced to ca 50%. The establishment of corridors and widening of grassland patches helps to restore the vegetation, and animals can spread the species over the restored area. The period between the restoration years should be inversely proportional to the amount of preserved grassland characteristic herb layer.

Management of Juniper Shrublands

The general Natura 2000 Habitats Directive manual does not include any instructions on the management of Juniper communis formations (5130). The juniper shrubland habitat type may be of natural origin in several cases, but if the juniper coverage has reached 80% it is not reasonable to manage the community anymore and one must decide whether to leave the area to develop naturally or to restore it as grassland. Juniper shrubland with dense juniper cover and small number of other plant species is not a climax community, on the event of the death of the first generation junipers; the progeny is not able to compete with fast-growing broad-leaved trees or pines. Succession will inevitably lead to the formation of a more species rich alvar forest, while grazing and/or tree removal will only postpone this a little.

Management of Juniper Shrublands Formed on Alvar Grasslands

One must assume the viewpoint that the management (tree removal, grazing) of an alvar shrubland is no longer reasonable if the community type has been determined correctly with regard to such areas. If one wishes to manage this kind of area (by grazing), one must restore the area as an open alvar first and assess the successfulness of the restoration beforehand.

Management of the Other Type of Juniper Shrublands

The classification and management instructions for the other type of shrublands differ from those imposed on alvar shrublands. Alvar shrublands are former alvar grasslands and if the juniper coverage is less than 80%, the areas should be classified as alvars in need of restoration. Juniper covered communities which have developed from dry and fresh grasslands, boreal heath grasslands or boreal grasslands can be classified as shrublands even at 30–80% coverage and preserved as a (possibly open) managed shrubland (5130). In short, one must consult with the landowner in the case of the other type of shrublands and decide together whether to - preserve the area as a non-managed continuous shrubland (code 5130), juniper coverage >80%, no management subsidy)- preserve the area as a managed shrubland, remove junipers every now and then in order to maintain a suitable coverage (5130, coverage 30–75%, management subsidy)- restore the area according to its former condition, either to a managed dry and fresh grassland, boreal heath grassland or boreal grassland (coverage <30%, restoration subsidy, management subsidy).

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Table 1. Classifying areas as alvars or Juniper shrublands.

Habitat Open alvarAlver in danger of overgrowing

Overgrown alvar with a urgent restoration need Juniper shrub Alvar forest

Area covered by junipers 10-30 (40)% 40-50%

50-75% (80% in the conditions where the grass layer is present) 80-100%

less juniper shrub, more pine trees (also spruce, birch)

Herb layer

species rich herb layer present, consists of grassland species

species rich herb layer present, grassland species dominant in the herb layer

grassland characteristic herb layer present in patches, some areas are covered by moss or sparse vegetation

herbaceous vegetation species-poor and sparse, no dense herb layer, topsoil is covered by needle-fall and moss

herb layer consists of forest species

Necessary activity grazing

grazing, removal of trees/shrubs when necessary

restoration (removal of trees/shrubs) and then grazing

can be restored if reasonable, conservation of juniper shrub is not sustainable in long term

no human activity is necessary for alvar forest conservation

>>>>>>>>>Succession proceeds in this direction if the management stops>>>>>>>>>>

Table 2. A selection of light-demanding grassland species, which are rarely or not at all found on overgrown alvars. The list is informative and incomplete. Acinos arvensisAnthemis tinctoriaArtemisia campestrisArtemisia rupestrisCarex ornithopodaCarex caryophylleaCrepis tectorum

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Helianthemum nummulariumLeontodon autumnalisLibanotis montanaLinum catharticumOphrys insectiferaOrchis militarisPhleum phleoidesPolygala comosaPolygala vulgarisRanunculus bulbosusSagina nodosaSaxifraga tridactylitesSedum acreSedum albumThymus serpyllumVeronica spicataVincetoxicum hirundinariaViola hirta

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